Dryer drum

ABSTRACT

A drum structure for drying a sheet of material characterized by having means to control the heating profile along the length of the drum and thus control the amount of heat applied across the width of the web or paper being engaged by the drum. To control the heating profile, the rate of heat transfer of the heating medium such as steam is varied along the axial length of the drum by selectively mixing a non-condensible medium with the heating medium to reduce the rate of heat transfer. In one embodiment of the drum structure, the drum is provided with a plurality of subchambers formed by axially spaced interior partitions which subchambers enable control of the rate of heat transfer to the drum surface associated with each sub-chamber. In another embodiment, the inner surface of the drum is provided with axially spaced grooves and the drum has a second header for a non-condensible medium, which header has means to introduce the non-condensible medium to each groove to control the rate of heat transfer at the groove.

United States Patent Duane [451 July 11, 1972 54} DRYER DRUM [57]ABSTRACT [72] Inventor. Robert A. Deane, Rockford, Ill.

A drum structure for drying a sheet of material characterized 1Asslgneei mm by having means to control the heating profile along thelength 22 Fred: N of the drum and thus cotrol the amount of heat appliedl l M acres the width of the web or paper being engaged by the [21]Appl. No.: 88,930 drum. To control the heating profile, the rate of heattransfer of the heating medium such as steam is varied along the axiallength of the drum by selectively mixing a non-condensible [52] US. Cl...34/4l, 34/124,l|665 /9l(S medium with the Mining Mum m reduce the rateof heat s I] in CI mb 5 transfer. in one embodrme' nt of the drumstructure, the drum is provided with a plurality f mh b f d b i ll [58]dd mil "34/41, I I9, [24, 165/90, 9| spaced inerior partitions whichsubchambus bk ni l Rd of the rate of heat transfer to the drum surfaceassociated with each sub-chamber. In another embodiment. the innersurface UNITED TATES of the drum is provided with axially spaced groovesand the s PATENTS drum has a second header for a non-condensible medium,3,492,741 2/1970 Witworth .3411 24 which header has means to introducethe non-condensible 1,594,718 8/1926 Fulton ....34ll24 medium to eachgroove to control the rate of heat transfer at 2,792,643 5/l957 Guy....34Il24 the groove. 3.241.251 3/1966 Justus et a1. ..34/124 PrimaryExaminer-Carroll B. Dority. Jr. 8 Clairm, 3 Drawing figures ArtomeyHill,Sherman, Meroni. Guns 8: Simpson /2 I 1 .zz I I 1 I 1 I I I I I l i i t/7 /l PMENTEDJ L 11 I972 3.675 337 sum 2 nr 2 Fig-'3 DRYER DRUMBACKGROUND OF THE INVENTION 1 Field of the Invention The presentinvention is directed to a dryer drum and a method of drying sheetmaterial and particularly a web of paper material.

2. Prior Art In presently known devices for drying paper webs or sheetsof material, the paper web or the sheet of material is engaged acrossits width by one or more internally heated drying drums. For variousreasons, the drying device does not dry the aper webs across its widthwith a uniform rate of drying.

SUMMARY OF THE INVENTION The present invention is directed to a dryerdrum structure and a method of drying sheet material which utilizesmeans for controlling the heating profile along the axial length of thedrum so that the heat applied across the width of a sheet of paper webby the drum can be controlled to obtain a desired drying profile acrossthe web of paper being dried by the drum. In one embodiment of theinvention, the means for control are a plurality of axially spacedpartitions forming a plurality of sub-chambers in which the rate of heattransfer of each sub-chamber can be controlled to control the rate ofheating of the drum surface. ln another embodiment of the presentinvention, the means for controlling includes a plurality of axiallyspaced grooves on the inner surface of the drum with means for supplyinga non-condensible medium to the grooves to change the rate of heattransfer in the particular grooves.

Accordingly, it is an object of the present invention to provide a dryerdrum having means for controlling a heating profile along the axiallength of the drum.

Another object of the present invention is to provide a method of dryingsheet material including controlling the profile of the rate of dryingof the material across its width.

Other objects, features and advantages of this invention will be readilyapparent from the following description of the preferred embodimentstaken together in conjunction with the accompanying drawings, althoughvariations and modifications may be effected without departing from thescope and spirit of the novel concept of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a cross sectional view takenalong the axis of one embodiment of the dryer drum of the presentinvention;

FIG. 2 is a partial axial cross section of another embodiment of thedryer drum of the present invention; and

FIG. 3 is a view with portions in elevation for purposes of illustrationtaken along the line III-III of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the principles of thepresent invention are of utility for controlling the heating profile ofany hollow heating unit, the principles are particularly useful whenincorporated in a dryer drum, generally indicated at 10, as illustratedin FIG. 1, utilized to dry at web of paper II during paper makingoperation.

The dryer drum I has a cylindrical shell 12 which contacts the sheet ofmaterial or web of paper II during the drying of the material. The shell12 at each end has an end plate I3 which is secured to the shell byconventional means such as bolts 14 to define an internal chamber I5.Each of the end plates 13 has a hub portion 16 having bearing surfaces17 which receive support means for supporting the drum for rotation andthe hub may include means for connecting the drum to a source ofrotational movement.

To heat the dryer drum I0, a steam conduit or pipe 18 extends along theaxis of the drum 10. As illustrated, pipe I8 has a plurality of steamnozzles 19 axially spaced therealong and the pipe is supported bybearing means 21 in each of the end plate hubs 16. To prevent the lossof steam from the chamber 15. seal means 22 is provided at the end ofone hub and seal means 23 is provided at the end of the other hub tosealingly engage each end of the conduit 18. The bearing means 2I enablethe drum I0 to rotate relative to the pipe 18 and thus the pipe 18, asillustrated, is stationary.

The pipe 18 is connected adjacent the seal means 23 to a supply pipe 24extending to a source of heat transfer steam. At the other end adjacentthe seal means 22, the steam pipe or conduit 18 receives a drain line 25which extends concentrically through the pipe to substantially thecenter of the chamber 15 where it is connected to a drain means 26 fordraining condensate from the chamber 15. The drain means 26 can be asiphon-type drain means and an example of siphon-type drain means isillustrated and described in the U.S. Pat. No. 2,993,282, issued to R.A. Daane and E. J. Justus on July 25, I961.

The steam passed through the nozzles 19 heats the cylindrical shell 12and the end plates 13 and in the process of heating forms a condensate.The condensate due to the speed of rotation of the drum I0 accumulatesas a cylindrical layer adjacent to the interior surface 27 of the shell11. The siphon or drainage means 26 due to the difference in pressure inthe chamber 15 and the pressure in the drain line 25 siphons thecondensate from the chamber 15.

When drying a web of paper II with a dryer drum, the rate of dryingacross the width of the web is not always uniform. For example, the edgeportions of the web may dry at a faster rate than the center portion.

To control the rate of drying across the web of the paper, the drum I0is provided with means for controlling the profile of heating along theaxial length. As illustrated in FIG. I, the means for controllingincludes a plurality of axially spaced partitions 28 which are attachedto the steam pipe I8 to sub divide the chamber I5 into threesub-chambers, a center subchamber 30 between the two partitions 28, andan end subchamber 31 adjacent each of the end plates I3. Each of thepartitions 28 is provided with peripheral openings 33 which areillustrated as an annularly extending space between the peripheral edgeof the partition 28 and the inner surface of the shell 12.

The means for controlling the profile of heating also includes means forintroducing a non-condensible medium such as air into predeterminedsub-chambers such as 31. As illus trated, the means for introducing airincludes an air supply line 35 extending inwardly from each end of thesteam pipe I8 with such line 35 terminating at an air nozzle 36 thatdischarges into a chamber 31. Each of the air supply lines 35 isconnected to a source of air under pressure and has a valve 37 forcontrolling the amount of air flowing through the line 35 and the nozzle36 which air is heated by steam in the pipe I8.

By adding a non-condensible medium such as air to the chamber 31 andallowing it to mix with the steam entering through the nozzle I9, theefficiency of the heat transfer of the steam heating the shell I2 isreduced. Thus the adding of air to the chamber 31 lowers the rate ofheat transfer to the portion of the shell I2 which is associated withthe chamber 31.

The partition 28 maintains the steam or steam and air mixture in each ofthe sub-chambers 30 and 31; however, the openings 33 allow a portion ofcondensate to move between the chambers and to the system 26 for removalfrom the drum. The size of the openings 33 and their coaction with thecondensate in each of the sub-chambers 30 and 31 limit the flow of thesteam or steam and air mixture across the partition 28 and between thesub-chambers. Thus the heating medium in each of the sub-chambers 30 and31 is substantially isolated from the heating medium in the adjacentsub-chambers and rate of heating to the portion of the shell I2associated with each sub-chamber can be controlled and made differentfrom the rate of heating in the other sub-chambers. Thus, by controllingthe heating characteristics of the heating medium in each sub-chamber bycontrolling the amount of air added to the heating medium, will vary theheating profile along the axial length of the dryer drum l0.

In the dryer drum of FIG. I. only the sub-chamber 31 has air nozzles 36.By adding air to the heating medium in each sub chamber 31. the rate ofheat transfer in the sub-chamber can be reduced below the rate of heattransfer in the center subchamber 30. By changing the rate of heattransfer, the end portion of the shell associated with the sub-chamber31 will receive the heat of the steam at a lower rate than the centerportion and thus a web of paper 11 which is being engaged by the dryerdrum l will have more heat applied to its center portion than to itsedge portion. By selecting different rates for heat transfer, theheating profile of the roll along its axial length can be controlled sothat the rate of drying of the web or paper ll will be substantiallyuniform across its width.

As illustrated. the steam pipe 18 supporting the steam nozzles 19, thedrain means 26 and the drain line 25 along with the air lines 35, airnozzles 36 are stationary with respect to the rotating shell 12 and endplates 13 of the dryer drum 10. If desired, the end structure of thepipes 18 along with the drain line 25 and the air lines 35 can beprovided with appropriate connections to enable relative rotation sothat the structure disposed in the chamber of the dryer drum rotateswith the dryer drum. If the partitions 28 and steam pipe 18 rotate withthe shell 12, the partitions can be provided with connections to theinner surface 27 of the shell 12 to provide additional supports.However. if the partition and the steam pipe 18 are stationary, theperipheral clearance such as the peripheral opening 33 is required toenable the relative rotation between the drum shell ll and the partition28.

Although only two partitions 28 are illustrated to create threesubchambers. additional partitions could be used to increase the numberof sub-chambers. Each sub-chambers can be provided with means for addinga non-condensible medium such as air and means to control the amount ofair added could be provided for each of the sub-chambers.

Another structural embodiment of a dryer drum having means forcontrolling the heating profile along the axial length of the drum isgenerally indicated at 50 in F165. 2 and 3 and has a cylindrical shell51. The drum 50 can either be constructed with a structure similar tothe drum 10 of FIG. 1 with end plates, steam lines. air lines and drainlines or constructed with a structure similar to the drum illustratedand disclosed in U.S. Pat. No. 3,241.25 l issued to E. l. Justus and R.A. Daane on Mar. 22, l966.

The shell 51 has a plurality of axially spaced grooves 52 on the innersurface and the steam condenses in the grooves 52 to heat the portion ofthe shell 5] associated with each of the grooves. Each groove 52 has a aroot surface 53 and radially extending side walls 54.

To remove the condensate from the grooves, a drain means having a header55, which is connected by a conduit 56 to a drain line of the drum has aplurality of small tubes 57 with a tube extending into each of thegrooves 52. The small tubes 57 remove the condensate from each of thegrooves 52 and the condensate is then drawn into the header 55 and thenthrough the conduit 56 to the drain line.

To control the heating profile along the axial length of the drum 50, asecond header 60 which is connected by a conduit 61 to a source ofnon-condensible medium such as air supplied to the interior of the drum50 by an air line similar to 35 of FIG. I. is provided and extendsparallel to the axis of the drum 50. The header 60 has a plurality ofaxially spaced tubes 62 which are arranged with one tube extending intoeach groove 52. The tubes 62 act as an air nozzle for discharging airinto each groove 52 at the root surface 53. The air discharged into thegroove 52 will be concentrated at the root surface 53 and the side walls54 of the groove will limit the fiow of the air into the adjacentgrooves. By appropriate means such as providing a construction in thetubes 62, the amount of air discharge from each tube 62 into itsrespective groove 52 can be selectively varied.

As in the previously described embodiment, the addition of air to thesteam in the grooves 52 will lower the rate of heat transfer and enablea change in the amount of heat transferred through the root surface 53to the shell 51 adjacent the groove 52. By varying the amount of airdischarged into each groove 52, the heating profile of the shell 51 canbe varied. Thus. by arranging each tube 62 to discharge the desiredamount of air for a given air pressure in the header 60, the heatingprofile along the length of the drum 50 can be controlled to be apredetermined profile which is best suited to achieve the desireduniformity of drying of the web of paper.

Although minor modifications might be suggested by those versed in theart, it should be understood that I wish to embody within the scope ofthe patent warranted hereon all such modifications as reasonably andproperly come within the scope of my contribution to the art.

I claim as my invention:

1. A dryer drum comprising:

a cylindrical shell;

end plate heads secured to the shell to provide a closed chamber;

means for supporting the drum for rotation;

means for delivering heat transfer steam to the chamber along the axiallength thereof; and

means for controlling the heating profile along the axial length of theshell including means for supplying a noncondensible medium topredetermined portions of the closed chamber to lower the rate of heattransfer of the steam in the predetermined portions.

2. A dryer drum according to claim 1. wherein said controlling meansinclude means dividing said chamber into a plurality of sub-chambers andwherein said means for supplying a non-condensible medium introduces thenon-condensible medium to predetermined sub-chambers to lower the rateof heat transfer of the steam in the predetermined sub-chambers.

3. A dryer drum according to claim 2. which further include means forremoving condensate from the inner surface of the shell and said meansfor removing condensate is disposed in the sub-chamber which is equallyspaced from each of said end plates and said means dividing said chamberincludes means enabling transfer of condensate between the su b-chamberswhile limiting the transfer of the steam and non-condensible mediumbetween said sub-chambers.

4. A dryer drum according to claim 2, wherein said means dividing saidchamber comprises:

partitions extending transverse to the axis of said shell. saidpartitions having means defining openings adjacent the inner surface ofsaid cylindrical shell for transfer of condensate between thesub-chambers whereby during operation, the condensate in saidsub-chambers blocks said opening means to limit the flow of steam andnoncondensible medium across said partitions.

5. A dryer drum according to claim 1, wherein said controlling meansincludes a plurality of axially spaced grooves provided on the innersurface of the cylindrical shell and wherein said means for supplying anon-condensible medium is arranged to introduce the non-condensiblemedium at a predetermined rate to each of said grooves so that the rateof heat transfer at each of the grooves is varied by the rate ofintroduction of the non-condensible medium thereto.

6. A dryer drum according to claim 5, wherein each of the grooves isprovided with means for removing the condensate therefrom.

7. A dryer drum according to claim 5, wherein said means for supplying anon-condcnsible medium includes a header disposed in the chamber andextending parallel to the axis of the shell. said header being connectedto a source of non-condensible medium and having a plurality of tubesextending therefrom, each of said tubes extending to one of the groovesand terminating adjacent the root thereof so that the non-condensiblemedium can be discharged adjacent the root of the respective groove.

8. A method of drying a web of sheet material by surface contact with asteam heated, horizontally disposed rotating cylinder drum comprisingthe steps of heating the cylinder drum by distributing steam to theinterior of the drum to provide a supply of uncondensed portions tolower the rate of heat transfer at these portions to obtain the desiredheating profile along the length of the drum to insure the desiredapplication of heat across the width of the web of material to controlthe rate of drying across the width of the web of material.

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1. A dryer drum comprising: a cylindrical shell; end plate heads securedto the shell to provide a closed chamber; means for supporting the drumfor rotation; means for delivering heat transfer steam to the chamberalong the axial length thereof; and means for controlling the heatingprofile along the axial length of the shell including means forsupplying a non-condensible medium to predetermined portions of theclosed chamber to lower the rate of heat transfer of the steam in thepredetermined portions.
 2. A dryer drum according to claim 1, whereinsaid controlling means include means dividing said chamber into aplurality of sub-chambers and wherein said means for supplying anon-condensible medium introduces the non-condensible medium topredetermined sub-chambers to lower the rate of heat transfer of thesteam in the predetermined sub-chambers.
 3. A dryer drum according toclaim 2, which further include means for removing condensate from theinner surface of the shell and said means for removing condensate isdisposed in the sub-chamber which is equally spaced from each of saidend plates and said means dividing said chamber includes means enablingtransfer of condensate between the sub-chambers while limiting thetransfer of the steam and non-condensible medium between saidsub-chaMbers.
 4. A dryer drum according to claim 2, wherein said meansdividing said chamber comprises: partitions extending transverse to theaxis of said shell, said partitions having means defining openingsadjacent the inner surface of said cylindrical shell for transfer ofcondensate between the sub-chambers whereby during operation, thecondensate in said sub-chambers blocks said opening means to limit theflow of steam and non-condensible medium across said partitions.
 5. Adryer drum according to claim 1, wherein said controlling means includesa plurality of axially spaced grooves provided on the inner surface ofthe cylindrical shell and wherein said means for supplying anon-condensible medium is arranged to introduce the non-condensiblemedium at a predetermined rate to each of said grooves so that the rateof heat transfer at each of the grooves is varied by the rate ofintroduction of the non-condensible medium thereto.
 6. A dryer drumaccording to claim 5, wherein each of the grooves is provided with meansfor removing the condensate therefrom.
 7. A dryer drum according toclaim 5, wherein said means for supplying a non-condensible mediumincludes a header disposed in the chamber and extending parallel to theaxis of the shell, said header being connected to a source ofnon-condensible medium and having a plurality of tubes extendingtherefrom, each of said tubes extending to one of the grooves andterminating adjacent the root thereof so that the non-condensible mediumcan be discharged adjacent the root of the respective groove.
 8. Amethod of drying a web of sheet material by surface contact with a steamheated, horizontally disposed rotating cylinder drum comprising thesteps of heating the cylinder drum by distributing steam to the interiorof the drum to provide a supply of uncondensed steam in intimate contactwith substantially the entire interior surface of the drum; withdrawingthe condensate from the interior of the drum; and controlling the rateof heat transfer of the steam to the drum at predetermined axialportions by introducing a non-condensible medium to some of thepredetermined axial portions to lower the rate of heat transfer at theseportions to obtain the desired heating profile along the length of thedrum to insure the desired application of heat across the width of theweb of material to control the rate of drying across the width of theweb of material.